Key takeaways: 

• The RateFlow API supports Optimal Blue, Loansifter, Mortech, Polly, Lender Price, and the PPE from ICE. 
• As a pricing engine-agnostic tech connector, it helps you pull live rates to your website — and makes sure those are rates you can actually offer. 
• The right pricing engine to use with RateFlow depends on your lending institution’s specific needs. 
• Configuring RateFlow with your pricing engine usually only takes a few days. 

If you’ve spent any time shopping for a mortgage rate API, you’ve probably noticed that one big question shapes everything: "Where do the rates come from?" Rates are only as accurate, competitive, and compliant as the pricing engine behind them.

RateFlow, BankingBridge's mortgage rate API, is built as a pricing engine-agnostic layer. That means it connects to the engine(s) your institution already uses, pulls live rate data from your actual investors and product set, and delivers it to your website, app, or lead generation flow in a consistent, standardized format.

Here’s a full breakdown of every pricing engine RateFlow currently supports, what each one is, and which type of lender it is best suited for.

Optimal Blue

Best for: Mid-sized to enterprise mortgage lenders, banks, and correspondent investors

Optimal Blue is the most widely used mortgage pricing engine in the United States, powering pricing for thousands of lenders and connecting to hundreds of investors. It’s the backbone of much of the secondary market, providing real-time Best Execution pricing, lock desk functionality, and deep investor coverage across conventional, FHA, VA, USDA, jumbo, and non-QM products.

RateFlow's Optimal Blue integration supports:

• Standard conventional, FHA, VA, USDA, and jumbo pricing
• ARM products, including 5/1, 7/1, and 10/1 structures
• Affordable products including HomeReady and Home Possible via the “include_affordable_products” parameter
• Borrower-paid MI and lender-paid MI scenarios
• Lock period selection
• Automated underwriting system (AUS) specification (DU, LP, or Not Specified)
• Fees-in pricing via the “feesIn” parameter through the LodeStar fee engine integration
• Multi-investor search across all available investors simultaneously

Optimal Blue is the right choice for lenders who want the broadest investor coverage, the most granular product eligibility rules, and the most widely recognized pricing data in the industry. If your lock desk runs on Optimal Blue and you use RateFlow, your website rates will match your lock desk rates exactly.

Loansifter (Powered by Optimal Blue)

Best for: Mortgage brokers, smaller correspondent lenders, and lenders who need a lighter Optimal Blue footprint

Loansifter is Optimal Blue's broker-facing product search and pricing tool, designed specifically for mortgage brokers and smaller lenders who need access to Optimal Blue's investor network without the full suite of enterprise features. It provides the same core rate data and investor coverage as Optimal Blue's enterprise platform, delivered through a streamlined interface and API.

RateFlow's Loansifter integration supports the same core parameters as Optimal Blue:

• Conventional, FHA, VA, USDA, ARM, and jumbo pricing
• Investor search and product eligibility
• Lock period and AUS options
• Credit score, LTV, and loan purpose parameters

For mortgage brokers in particular, using Loansifter with RateFlow provides a direct path to displaying live wholesale rates on their website — the same rates their borrowers could get through any channel — without building a custom pricing integration from scratch.

Mortech

Best for: Independent mortgage bankers, retail lenders, and lenders on the Zillow ecosystem

Mortech is a Zillow-owned mortgage pricing and product eligibility engine used by thousands of independent mortgage banks and retail lenders across the country. It offers strong coverage of conventional, FHA, VA, and USDA products with deep integration into the Zillow consumer mortgage ecosystem.

RateFlow's Mortech integration supports:

• Conventional, FHA, VA, and USDA pricing
• Standard purchase and refinance scenarios
• Credit score, LTV, and property type parameters
• Lock period options
• Loan officer-level pricing through the LOID parameter

Mortech is a natural fit for lenders who are already embedded in the Zillow ecosystem or who use Mortech as their primary pricing and lock desk system. RateFlow connects directly to your existing Mortech credentials, meaning the rates on your website reflect your actual Mortech pricing, not a third-party approximation.

One distinctive feature of the Mortech integration is its connection to Zillow's consumer rate data. This gives lenders insight into how their pricing compares to the market benchmarks their borrowers are already seeing.

Polly

Best for: Technology-forward lenders, non-QM specialists, and lenders looking for a modern cloud-native pricing platform

Polly is one of the newer entrants in the mortgage pricing engine space, but it has grown rapidly among lenders who prioritize a modern, API-first architecture. Built cloud-native from the ground up, Polly offers pricing and hedging in a single platform with real-time rate sheet management, investor connectivity, and deep product eligibility functionality.

RateFlow's Polly integration supports:

• Conventional, FHA, VA, USDA, jumbo, and non-QM pricing
• Real-time rate sheet updates as investors reprice
• Full product eligibility engine with granular guideline enforcement
• Lock period and scenario-based pricing
• Support for Polly's expanded non-QM and expanded credit product sets

Polly is a strong choice for lenders who have made the strategic decision to modernize their technology stack and want a pricing engine that matches their investment in digital infrastructure. Its API-first design means RateFlow's integration is particularly clean. Rates flow through reliably and quickly, with fewer of the latency issues that can affect older pricing platforms.

For lenders offering non-QM or expanded credit products, Polly's support for those product types through RateFlow creates an opportunity to display non-QM rates on a website. That’s something very few lenders are currently doing and a genuine competitive differentiator.

Lender Price

Best for: Mortgage brokers, wholesale lenders, and multi-channel lending operations

Lender Price is a pricing and product eligibility platform built specifically for the wholesale mortgage channel. It’s used extensively by mortgage brokers and wholesale lenders who need to manage pricing across multiple broker relationships, investor channels, and product types simultaneously.

RateFlow's Lender Price integration supports:

• Conventional, FHA, VA, USDA, jumbo, and ARM pricing
• Multi-lender and multi-investor search via the “searchAllInvestors” parameter
• Borrower-paid MI (BPMI) and lender-paid MI options
• MI company specification (e.g., Arch MI) via the “miCriteria” parameter
• Lock period and AUS options
• Closing cost integration via “useCompanyDefaultClosingCost”
• Purchase and refinance scenarios including cash-out refinance

Lender Price is particularly well-suited for broker-focused operations where the borrower is comparing rates across multiple wholesale lenders simultaneously. RateFlow surfaces those comparisons in a clean, consumer-friendly format. That turns what’s normally a complex back-office function into a simple rate shopping experience on the front end.

One thing worth noting from our integration experience: Lender Price validates that purchase price, loan amount, and down payment amount are internally consistent. Sending a down payment amount of zero when the purchase price and loan amount imply a down payment will not necessarily cause a failure, but sending a loan amount that exceeds the purchase price will. Accurate inputs produce accurate rates. Always verify that your loan scenario math is consistent before sending a request.

Encompass Product and Pricing Engine (EPPS), aka ICE PPE

Best for: Lenders running ICE Mortgage Technology's Encompass LOS

Encompass Product and Pricing Engine (EPPS), also known as ICE PPE, is ICE Mortgage Technology's native pricing engine. As you would probably expect, it’s deeply integrated into the Encompass loan origination system. For lenders who run their entire origination workflow on Encompass, EPPS/ICE PPE is the natural pricing choice because rates, product eligibility, and lock requests all flow directly within the LOS without requiring a separate system integration.

RateFlow's EPPS/ICE PPE integration supports:

• Conventional, FHA, VA, USDA, jumbo, and ARM pricing
• Full integration with Encompass loan file data
• Rate and product eligibility tied directly to the Encompass product and pricing channel configuration
• Lock period and scenario pricing
• Purchase, refinance, and cash-out scenarios

The EPPS/ICE PPE integration is particularly valuable for lenders who want their website rate display to be a true reflection of what borrowers will see when a loan officer pulls pricing inside Encompass. Because it’s the same engine driving lock desk pricing in the LOS, there’s no gap between the "teaser rate" on the website and the actual rate the borrower receives in a loan estimate. This gives you a transparency advantage that builds borrower trust and reduces friction in the application process.

For lenders on the Encompass ecosystem, the EPPS/ICE PPE integration through RateFlow also creates a natural path to connecting website leads directly to Encompass workflows, with rate data that’s already consistent with the LOS from the first touchpoint.

How RateFlow handles multiple pricing engines

There’s one big practical advantage in building on RateFlow rather than integrating directly with a pricing engine. RateFlow normalizes the output from all six engines into a single, consistent response format.

Each pricing engine has its own request schema, response structure, authentication method, and quirks. Optimal Blue uses OAuth with client credentials and returns rate data in its own proprietary format. Loansifter has a different endpoint and parameter structure. Mortech uses API key authentication. Lender Price has specific validation rules around down payment consistency. Polly's cloud-native architecture means faster response times but different field names.

RateFlow handles all of that complexity under the hood. Your integration — whether it’s a website rate widget, a mobile app, or an internal rate tool — sends a single, standardized request and receives a single, standardized response. That’s true regardless of which engine is running on the back end.

This also means that if your institution changes pricing engines, your front-end rate experience doesn’t need to be rebuilt. This transition happens more often than most people expect, especially as lenders grow or change investors. If you make a change, all you have to do is update your RateFlow configuration. Your website keeps working with next-to-no downtime.

Choosing the right pricing engine 

Choosing the Right Pricing Engine for Your Integration

If you’re evaluating RateFlow and trying to decide which pricing engine to connect to, we have a couple of considerations.

What all six have in common

Regardless of which pricing engine you connect to, every RateFlow integration shares the same core capabilities:

• Real-time pricing. Rates aren’t cached from this morning's rate sheet or averaged across investors. Instead, they’re pulled live at the moment a borrower requests them. When rates move, your website moves with them.
• Loan officer-level pricing. Every request is tied to a specific loan officer ID (LOID). That means the rates a borrower sees on your website are the actual rates that loan officer can offer, instead of a generic market average.
• Full product coverage. RateFlow supports the full product mix your borrowers need to make an informed comparison: conventional, FHA, VA, USDA, jumbo, ARM, and, in some cases, non-QM.
• Consistent request and response format. One integration, six engines. Your developers build once and gain access to all supported pricing engines without rebuilding from scratch.
• BankingBridge support. Every integration comes with BankingBridge's implementation support, documentation, and ongoing technical assistance. Why? Because we know from experience that the details in a pricing engine integration matter. Getting them right from the start saves significant time.

Picking your pricing engine

Since RateFlow means you can expect some consistency in how rates flow from your pricing engine, you need to look for differentiators elsewhere. Here’s a simple framework to help point you in the right direction:

If you’re not sure which engine is right for your institution, start with whichever one you’re already paying for. The fastest path to live rates on your website is connecting RateFlow to the pricing engine you already use. No new vendor relationship, no new credentialing process, no new rate sheet management. You already have the rates. RateFlow puts them on your website.

Getting started with RateFlow

If you’re ready to connect your pricing engine to your website, the process starts with a conversation. Our BankingBridge team will confirm your pricing engine credentials, review your product set, and configure your RateFlow account. All of that typically only takes a few business days.

From there, you have two paths: embed the BankingBridge rate widget on your existing website with a single script tag, or integrate RateFlow's API directly into your custom application. Either path can have live rates on your website within a week.

Ready to get started? Book a demo with our team today.

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